A. S. Van Jaarsveld

It's time to work together and stop duplicating conservation efforts ...

We strongly support initiatives to produce clear, efficient and practical goals for conservation to guide biodiversity planners and decision-makers in governments, agencies, conventions and non-governmental organizations (NGOs). However, as things stand there is only limited consensus on global conservation priorities at international level. We believe that the time is now right for scientists and practitioners to work together to develop a commonly adopted blueprint for action.

The use of land facets as biodiversity surrogates during reserve selection at a local scale

Abstract Where species distribution data are inadequate reserve selection procedures have to rely on surrogate measures of biodiversity. The informativeness of land facets (the simplest units of a landscape with uniform slope, soils and hydrological conditions) as a local scale environmental surrogate was investigated in the Venetia-Limpopo Nature Reserve, South Africa. Multivariate analysis (MDS, ANOSIM) revealed that the land facets adequately represent distinct bird and dung beetle assemblages and are therefore useful surrogates. These land facets/assemblages were subsequently used as attributes in the following reserve selection procedures: (i) Percentage Area Representation (PAR—represent a nominated percentage area of each assemblage); (ii) Species-Assemblage Representation (SAR—represent each species within the smallest number of assemblages); (iii) Assemblage Diversity (AD—maximising diversity by first selecting areas containing most dissimilar assemblages). The influence of grid cell size, target representation percentages and an over-representation constraint on the efficiency of the algorithms were illustrated. The SAR procedure did not represent assemblages lacking distinguishing species and were thus more efficient in terms of total area selected. The AD procedure selected a slightly larger area than the PAR procedure, but was highly effective at rapidly increasing the diversity of the reserve network.

An evaluation of the gradsect biological survey method

Biological surveys are necessary to gather species distribution data for the identification of priority conservation areas. The rationale of the gradsect method is that sampling (transects) oriented along the steepest environmental gradient should detect the maximum number of species in an area. The efficiency of the gradsect survey method was evaluated by comparing it to random, systematic and habitat-specific survey methods, during faunal field surveys (target groups: birds and dung beetles). Three gradsects were positioned within the study area to follow the major physiographical characteristics, incorporate all environmental strata (land facets) and yet be as logistically convenient as possible. The efficiency of survey methods was expressed as the number of species recorded per sampling unit effort and illustrated using bootstrap estimations to plot species accumulation curves. The gradsect method proved to be as efficient as the habitat-specific survey method and consiste ntly more efficient than the systematic and random surveys for both taxa sampled. The present study therefore illustrates that the gradsect survey method provides a cost-effective and swift representative sample of regional fauna. Moreover, the results indicate that land-form sequences, specifically ‘land facets’, are useful surrogates when sampling environmental diversity where distinct environmental gradients such as altitude and rainfall are absent.

Scale and conservation planning in the real world

Conservation planning is carried out on a variety of geopolitical and biogeographical scales. Whereas considerable consensus is emerging about the most appropriate procedures for identifying conservation areas, the spatial implications of conducting conservation planning at divergent scales have received little attention. Here we explore the consequences of planning at different geopolitical scales, using a database of the mammalian fauna from the Northern Provinces of South Africa. The conservation network resulting from treating the region as one unit is compared with networks generated separately for the provinces nested in that region. These outcomes are evaluated in terms of (i) their land use efficiencies, (ii) their spatial overlap, and (iii) the impact of algorithm attributes. Although land use efficiencies are greater on broader scales, on average the spatial congruence between the broad–scale regional network and fine–scale provincial networks was less than 14%. Algorithms using different selection rules fail to improve this disturbing outcome. Consequently, scale has an overwhelming influence on areas identified as conservation networks in geopolitical units. This should be recognized in conservation planning.

Nature reserve selection in the Transvaal, South Africa: what data should we be using?

Iterative reserve selection algorithms were applied to two mammal databases, generalized to sixteenth degree grid squares, for the Transvaal region of South Africa. Based on primary point data, 24 grid squares are required to represent all species at least once, while only 13 grid squares are required when based on distribution map data; only two of these grid squares are common to both analyses. As the number of representations per species is increased from one to five, the number of selected grid squares increased to 86 and 71 or 72 respectively, with only 17 of these common to both analyses. These differences in the selection of sites are further reflected in the degree of congruence between selected grid squares and existing conservation areas which is on average 63.3% for grid squares selected from the primary database and only 42.5% for those selected from the distribution map database. These results emphasize the importance of quality data input when evaluating regional reserve networks. Highly generalized distribution map data sets, on the one hand, are extrapolations of limited data sets and contain non-quantifiable levels of false-positives which could have significant implications if used for establishing regional reserve networks. On the other hand, although there are problems associated with the establishment of primary diversity databases, namely data currency and uneven and non-random sampling (leading to false negatives), they remain our most reliable option for assigning conservation value.

Evaluating population persistence of censused and unmanaged herbivore populations from the Kruger National Park, South Africa

Abstract The application of the Dennis et al. (Ecol. Monogr., 61, 1991) model to data from 12 herbivore populations from the Kruger National Park, South Africa, introduces ‘risk assessment’ procedures into the conservation management of free-ranging species. The model enables one to predict the probability of reaching an arbitrarily defined threshold population size using census figures from censused and unmanaged populations. It also provides an objective evaluation of population persistence based on past performance. Of the 12 species investigated, five (impala Aepyceros melampus, blue wildebeest Connochaetes taurinus, zebra Equus burchelli, white rhinoceros Ceratotherium simum, giraffe Giraffa camelopardalis) appear to be secure, four (kudu Tragelaphus strepsiceros, waterbuck Kobus ellipsiprymnus, warthog Phacochoerus aethiopicus, sable antelope Hippotragus niger) are vulnerable and three species (tsessebe Damaliscus lunatus, eland Taurotragus oryx, roan antelope Hippotragus equinus) are at risk of declining by an order of magnitude within 100 years. Therefore, within data limitations, the KNP appears not to offer sufficient suitable habitat for a number of herbivore species despite its considerable size, and a metapopulation approach may be required for the effective conservation of some species. The model also allows the principle of ‘complementarity’ to be extended beyond that of species composition. Objective evaluations of population persistence, of censused and unmanaged populations, as demonstrated here, mean that the principle of ‘population viability’ can help the design of efficient regional reserve networks.

Biodiversity Conservation: Uncertainty in predictions of extinction risk/Effects of changes in climate and land use/Climate change and extinction risk (reply).

Thomas et al. reply — We reconsider our estimates of climate-related extinction in the light of three questions raised by Thuiller et al., Buckley and Roughgarden and Harte et al.. We are able to confirm our original conclusion that climate change represents a major threat to terrestrial species.

A multicriteria approach to reserve selection: addressing long-term biodiversity maintenance

Existing complementarity-based reserve selection techniquesconcerned with maximal biodiversity representation within minimum landarea do not necessarily ensure the long-term maintenance ofbiodiversity. These approaches often ignore the maintenance of naturalprocesses, turnover of feature diversity and the need to minimisethreats within conservation areas. We address these three emergentissues in the identification of potential avian conservation areas inthe Northern Province of South Africa, by combining ordination andspatial autocorrelation analyses, as well as land transformation datainto complementarity-based reserve selection techniques. Existingconservation areas are biased and inefficient and complementarity-basedmethods do little to correct this skew. The inclusion of speciesassemblage structure as well as the underlying environmental gradientsensures a conservation area network that strives to maintain bothbiodiversity pattern and process. Spatial autocorrelation analysisallows for the identification of areas with high β diversity,important areas for the long-term maintenance of biodiversity. Theinclusion of land transformation data leads to viable conservation areanetworks and highlights areas of potential conflict between biodiversityconservation interests and human land-use issues. These combinedimprovements on complementarity-based reserve selection techniques bringus a step closer to ensuring the long-term maintenance of biodiversitywithin conservation areas in the northern province.

Towards conserving regional mammalian species diversity: a case study and data critique

Species richness maps were derived for the Transvaal region from two different databases, namely a primary point database based on actual survey records and a generalized distribution map database. It is shown that sixteenth degree grid square (= QDS in Lombard 1995) species richness maps based on these two data sets for the region are highly disparate, which may be attributed to overestimation of species distributions by distribution maps and uneven sampling reflected in the primary point database. The limitations and problems associated with the two databases are discussed. Of the 10% most species-rich grid squares based on distribution maps and primary point data, 33,3% and 12% respectively are fully encompassed by existing conservation areas and are well represented in the sixteenth degree grid square networks selected by two iterative reserve selection algorithms.

Scales and consequences of human land transformation on South African avian diversity and structure

Species diversity and community structure indices (richness, diversity and evenness) are typically derived from contemporary biological survey atlases to identify conservation areas or to determine macroecological-environment relationships. Surprisingly, there are few studies based on national taxa surveys that describe and measure the influence human disturbance patterns may have on these ecological measures. This study uses various spatial statistical methods to examine and model large-scale spatial structure in diversity, structure indices derived from a comprehensive bird atlas, and composite variables of environment and human land transformation. Data were derived from an atlas of South African birds and segregated into five vegetation biomes. For each sample location, environmental and land-use data were used to calculate composite environmental gradients in climate, topography and human land transformation. Semivariograms were used to detect large-scale trends and spatial scale, and Morans I statistic correlograms to test for large-scale spatial autocorrelation in detrended diversity indices. Ordinary least squares regressions for all biomes indicated a significant positive relationship between high levels of human transformation and species diversity, whereas high transformation had a significant negative influence on evenness. These same relationships held for the majority of biomes after the effects of environmental gradients were removed. The analysis also shows that in areas with favourable environmental resource levels, diversity for birds increases. These areas also tend to contain a large proportion of highly transformed land, and evenness decreases in the woodland, grassland, Karoo and fynbos biomes. This suggests that high-intensity transformation may bring in novel resources for birds not normally found in some of the biomes, with some species adept at exploiting these changes and reaching high densities with a tendency for assemblage structure to drift towards single species dominance. The results imply that species data derived from contemporary atlases may begin to demonstrate the effects of human influence on ecological measures rather than only indicating the effects of environmental variation on community structure.